The problem. This study seeks to determine the observable effects of acetylcholine, succinylcholine, d-tubocurarine, and quinine on tardigrades and to compare these effects to known mammalian reactions. Evidence of synergism or antagonism is sought by combining each drug compound with the other three individually. Procedure. Three species of tardigrades (Milnesium tardigradum, Hypsibius oberhauseri, and Macrobiotus richtersi) were subjected to serial dilutions and 4.0% to 0.0% (weight/volume) of each of the four compounds and their binary combinations. Observations were made through a 25x binocular dissecting microscope at the time periods: 15 minutes, 1 hour, and 5 hours. Controls were kept in distilled water and in spring water. All test animals were kept in a moist-chamber to avoid evaporation and subsequent concentration of the test solutions. Anesthesia was tested by returning affected anmials to spring water and watching for movement, indicating recovery. Findings. Contraction of the tardigrades' bodies and legs was brought about within an hour by a minimum of 0.4% acetylcholine or 1.6% succinylcholine. In that same time period the tardigrades were relaxed, with the bodies and legs fully extended, by 1.2% d-tubocurarine; but no change was seen with up to 2.0% quinine. By 5 hours, 0.8% quinine had caused a relaxation of the animals. Acetylcholine and succinylcholine were highly synergistic. Both quinine and d-tubocurarine sensitized the tardigrades to acetylcholine. D-tubocurarine delayed the action of succinylcholine. Small amounts of d-tubocurarine negated effects of 2.0% or less succinylcholine, causing no observable effects. Quinine casued a delayed sensitization of the tardigrades to succinylcholine. D-tubocurarine and quinine delayed and reduced the effectiveness of each other. The effect of these test solutions was anesthesia, not narcosis. This was demonstrated by the recovery of the affected tardigrades when they were returned to spring water.